Bridgeport J head

[kgarver]

I have just bought on Ebay a Bridgeport J head (step pully type). Since I only paid $200 for it I'm assuming that it will need to be rebuilt. Has anyone rebuilt theirs? What pointers can you share? Are there any manuals that really take you through a rebuild step by step? Not a normal 60 page Bridgeport maintaince manual but something really on J head test and tear down procedure? Where did you get parts? I have contacted High Quality Tools in Ohio and recieved their catalog. Where else can I find parts? Talking to Bridgeport they, or rather one of their field representatives, stated that the bearings were NOT CNC grade 7 precision bearings. Is that correct? HQT gets $300 for two bearings and they are not class 7 either!!! I will need a motor and a motor pully. They want $115 for a new motor pully. Any Ideas where they can be bought at the right price. HQT will also sell me a 3 phase motor for $250.00 with a reversing switch. Garunteed to fit and run but nothing else. I already have a 3HP VFD so a 3 ph. motor would be best.

[Thrud]

kgarver:

Compared to what they had originally, any modern high grade bearings should be fine. If you go with Class 7 make sure you get proper installation procedure from the bearing supplier to prevent damage. Before you go ape **** check it out first to see if it even needs rebuilding. Check the bore of the spindle for wear too.

I would just get a 3Ph. and use the VFD.

[kgarver]

Thurd
Thanks for the reply. I assume the worst of course and will check it out throughly before tearing it apart. What I know that I definately need at this point is a 1 to 1-1/2 HP 3 PH motor. I called BP and they wanted $579.00 plus shipping. High Quality Tools,Inc. wanted $525.00 plus shipping. This for a motor made by Reliance Electric. Not the original one made by US Motor Co. If I could get someone to measure their shaft diameter, KW measurements, and especially shaft length I could shop around for something that will fit. The BP tech. support folks told me that the frame was 56-12 but they would not tell me what the shaft dia., shaft length or KW dimension was. I know that this is propriatary information but Western civilization will probably not fall if this gets into the wrong hands!!!

So how about it all of you Bridgeport owners out there? How about helping me out? Actually any BP head from the flange down will most probably have the same dimensions.

I appreciate all the help that I can get.
Ken

[John Foster]

K-- Mine measures .749 and is 2 1/4 long. I think I saw some place that this motor only fits Bridgeport. Not much chance to find something that will fit if that is the case.
If I had this problem I would look at "C" face motors (is that right, motors that mount on the end?) and would look at making an adapter plate to fit the Bport. This would make a good article for the Homs Shop Machinist. John F.

[crypto]

I bought an old round-ram Bridgeport 20-25years ago. At the time of purchase I replaced the original (ND#5206 #5 Precision) bearings with electric motor bearings (22590) on the suggestion of the bearing distributor, much cheaper. I also replaced the brake block pieces, clock spring, v-belt, timing belt and timing belt pulley flange brass gasket or shim (a very thin brass circular shim). I bought the parts from a bridgeport distributor.

It is a noisy old timer at the highest speeds but still capable of accurate work. I prefer it to the newer v-ram for I don't have to stretch to reach the spindle nut, it fits my short height.

[John Stevenson]

Ken,
Don't know if this helps but the American motors seem stuck on large obsolete frame sizes.
If you can get a European motor on the metric frame sizes you can get a far cheaper motor and smaller to boot. I do a lot of modification work on motors and the Bridgeport conversion is one of them. I take a stock 2 hp 3 phase motor, about 70 UKp [ $ 105 ] modify the shaft to 3/4" dia by 2 1/2" long and then make a converson plate 1/4" thick to convert the metric B type flange [ face fitting ] to fit the Bridgy.
Total conversion cost is around 140 UKP [ about $200 ]

John S.

[kgarver]

John;
Thats the kind of inormation that I'm looking for!! Not being too conversant on metric spec. motors could you give me a little more information on brand name or serial numbers? The motor sellers over here tend to be only that. They need some kind of number or they become apoplectic. Especially when I tell them that this is a metric spec motor. Not Invented Here and all that.

Regards, Ken

[John Stevenson]

Ken,
Looked thru some spec sheets and a 2hp motor is based on a 90 frame size. That means its 90mm from base to shaft centre. Not quite relevant with a flange mount motor but they still base these on foot mounted motors.
Good metric spec guide is at:-
http://en.weg.com.br/asp/files/Aluminium_EU-EFI.pdf

You have a vast choice of makes as none of the European makers use the American frame sizes so they all use these metric frame motors. Makes are ABB, Brook, VEM, WEG, Fimec, Ghirri,

To give you an indication of size difference look at:-
http://homepage.ntlworld.com/machines/bridgy_motor1.jpg
This shows a standard varispeed Bridgeport fitted with a 1.5HP US motor. Propped up behind this so it's in the same scale is a Fimec 90 frame 2hp motor. You can also get these in the same size rated at 3 hp, called the enhanced range.
These aren't special, these are run of the mill, off the shelf motors we fit every day.

The varispeed bridgy motor plate is at:-
http://homepage.ntlworld.com/machines/bridgy_motor3.jpg
and shows this as a 145TY-4 frame size.
Going to Baldors web site this size equates to a metric 135 frame. In metric terms this is our 10hp size motor!!
Also looking at the metric motors on Baldors site they list the 90 frame motor in the pic at $382. WOW!!!!!!!!!!
I think offhand the list on these are about 120 UKP [ $180 ] and I reckon I buy these at about 70 UKP [ $100 ].

John S.

[JCHannum]

John, how do you extend the shafts? Do you press out and replace, or do you sleeve them?
The Bridgeport motor is a proprietary motor made for Bridgeport on a 145T frame. I would suspect that it has beefed up bearings on output side for increased overhung load, as well as extended shaft.

[John Stevenson]

JC,
The standard Bridgeport motor is just a standard motor with a different mounting plate. Same bearings as the others in the range. You can swop endplates if you get the same series motor.
To extend the shaft you support the rotor on a slave bearing and hold this in the fixed steady. The reason you use a slave bearing is the coolant will wash the grease out of the proper bearing. Part off the stub, centre drill and drill 1/16" under size, in this case 11/16". Usual depth I go on one of these is 2 1/2"
Then bore out to about 15 thou under size to true the hole up and finish ream to size. For the stub I use drill rod as it's bang on size and ground. Some shafts have a keyway and some have a flat for the grub screw machine these in first. Then I put two bands of straight knurl on, one at the end and one just less than 2 1/2" up so it goes inside the hole. Dab of loctite, press the shaft in and when it's set cross drill thru the large diameter behind the bearing for a spring pin.

I work for four local motor companies doing this sort of work and I guess over a year I must do anywhere between 100 and 200 rotors. So far I have never had one back and some have been right pigs to do.
Four pics below show a DC armature being repaired. Armatures are especially hard as the comm and rotor core are seperate. Only way to put a new shaft into a DC is to strip it, press both off, fit new shaft and rewind it. This is expensive. The armature in the pics is about 15 HP out of a travelling crane with a snapped shaft where it changes section. With a stub there is no change of section. This was two years ago and as far as I'm aware it's still in service. If it had of let go they would soon tell you {g}

Forgot to add it takes about an hour to hour and a half to do one of these so it's very cost effective.

http://homepage.ntlworld.com/machines/broken%20dc%20armature2.jpg
http://homepage.ntlworld.com/machines/broken%20dc%20armature3.jpg
http://homepage.ntlworld.com/machines/broken%20dc%20armature4.jpg
http://homepage.ntlworld.com/machines/broken%20dc%20armature5.jpg

John S.


[This message has been edited by John Stevenson (edited 08-04-2002).]

[JCHannum]

Thanks John, neat trick.
I worked quite closely with a motor repair shop about 20 years ago, only way for them was to press out and replace. This leads to a bunch of other problems with laminations and getting the rotor back exactly where it belongs.
The motor on my Rockwell mill may need replacing shortly. It is a C flange with extended shaft. I'll rest easier with this in hand.

[dnsbss]

Are you replacing the head on your existing machine? If so I am looking for parts from the old one if you are willing to part with them.